This invention relates to a process for the production of C.sub.1 -- to C.sub.6 --N-alkylpyrrolidones from succinic anhydride and C.sub.1 -- to C.sub.6 -alkylamines and/or, C.sub.1 -- to C.sub.6 --N-alkylsuccinimide.
N-alkylpyrrolidones are of importance as solvents and intermediates and can undergo a number of characteristic chemical reactions (Kirk-Othmer, Vol. 19 (1982), p. 514-520, GB-Pat. No. 1 192 670, GB-Pat. No. 1 358 862 and U.S. Pat. No. 3,634,346).
By following conventional methods, N-alkylpyrrolidones have been obtained from the corresponding N-alkylsuccinimides by electrochemical reduction (Beilstein E III/IV 21: 3245), from pyrrolidin-2-one and methanol on Al.sub.2 O.sub.3 (German Pat. No. 830,194), from dihydrofuran-2-one and methylamine (Beilstein E III/IV 21: 3145), from succinic acid by way of N-methylsuccinimide in the presence of Ra-Ni and dioxane at 200.degree.-215.degree. C. and 200-220 bar (Khim. Prom. 1963 (7): 491-492), or from succinimide in the presence of the alcohol corresponding to the desired alkyl group, on cobalt or nickel catalysts at 200.degree.-280.degree. C. and under a pressure of 200-300 bar (Russian Pat. No. 259,889), as well as the method according to DAS No. 1,620,191=U.S. Pat. No. 3,448,118=GB-Pat. No. 1 089 834 wherein succinic acid is reacted with alkylamine and hydrogen in the presence of Raney metals, Co, Ni, Ru or Pd catalysts at 200.degree.-300.degree. C. and under pressures of 50 bar. Contrary to the statements in the specification (column 3, line 3), the examples reveal that the process evidently cannot be performed without the use of a solvent or diluent (water or dioxane).
In the above-mentioned methods, yields of alkylpyrrolidone of at best 80% are obtained.
Starting with N-methylsuccinimide (Khim. Prom. 491-2, 1963), a yield of merely 71.6% is achieved on Raney Ni.